This invention relates to an anti-deterioration agent for food flavors comprising a specific coumarin derivative; a method for preventing deterioration of food flavors present in foods; and a food of which food flavors are prevented from deterioration.
It has been known for a long time that organic matter such as fat and oil suffers from denaturation by oxidation or heat to reduce or lose its essential properties. In order to solve this problem, a large number of antioxidants have been developed and reported to date. For example, BHT (2, 6-di-tert-butyl-p-cresol), ascorbic acid, tocopherol compounds, and the like have been used widely for their excellent antioxidant action.
Flavors are frequently added to foods to satisfy the present consumers tastes, but it has been pointed out that the food flavors added to foods undergo deterioration during the preparation or storage of the foods, resulting in reduction of the flavor or taste. Most of food flavors being organic, it has been attempted to use known antioxidants, such as BHT, xcex1-tocopherol or ascorbic acid, to prevent the food flavors from deterioration. However, BHT and xcex1-tocopherol are inadequate for the needs, and ascorbic acid causes browning of some foods. It has therefore been demanded to develop an agent for preventing deterioration of food flavors (hereinafter referred to as an anti-deterioration agent for food flavors, or more simply, as an anti-deterioration agent) which can prevent deterioration of food flavors without impairing the appearance of the food.
Methods of using chlorogenic acid (Beverage Japan, No. 179, p. 57 et seg. (1966)) or a specific ester (JP-A-9-227456) as an anti-deterioration agent for food flavors have been reported. However, the former method is disadvantageous in that chlorogenic acid should be used in a relatively large amount, a considerable increase of off components of the smell is observed as demonstrated in Comparative Examples hereinafter given, and chlorogenic acid tends to be decomposed by heat to give some odd taste to foods. The latter method needs the anti-deterioration agent in a relatively large amount to achieve a substantial effect on food flavor deterioration.
An object of the present invention is to provide a compound having excellent ability to prevent deterioration of food flavors present in foodstuffs. In particular it is an object of the invention to provide a compound which is easily miscible with a food and is not separated from a food and does not impair the taste or appearance of the food.
The present inventors have conducted extensive investigation for obtaining a naturally-occurring compound which has excellent properties of preventing deterioration of flavors present in foods. As a result, they have found that specific coumarin derivatives are excellent in preventing deterioration of food flavors. Having continued their study based on this finding, they have discovered compounds which are easily miscible with foods and hardly separated therefrom and do not impair the taste or appearance of foods.
The present invention provides an anti-deterioration agent for food flavors which comprises at least one coumarin derivative represented by formula (I): 
wherein R1 represents a hydrogen atom, a hydroxyl group or a methoxy group, and R2 represents a hydrogen atom or a hydroxyl group, provided that R1 and R2 do not represent a hydrogen atom simultaneously.
The coumarin derivative represented by formula (I) is preferably selected from 6,7-dihydroxycoumarin represented by formula (II) (aesculetin), 7,8-dihydroxy-6-methoxycoumarin represented by formula (III) (fraxetin), and 7,8-dihydroxycoumarin represented by formula (IV) (daphnetin): 
The anti-deterioration agent of the invention preferably comprises an olive plant extract containing the coumarin derivative, an extract of the bark of an ash tree (Aesculus turbinata) containing the coumarin derivative, or a perilla plant extract containing the coumarin derivative.
The invention further provides a method for preventing deterioration of food flavors present in a food which comprises incorporating the above-described anti-deterioration agent into the food.
The invention furthermore provides a food containing the above-described anti-deterioration agent.